On a typical piano there will be three pedals in the center by the floor. These pedals are used to change the sound and effects of the piano.
The most common pedal is the Damper pedal located to the right. When the damper pedal is pressed down it raises the dampers inside the piano off of the strings to allow the notes to continue to ring. Once the pedal is released the dampers return to resting position and the notes will cease to sound.

On a grand piano the Sostenuto pedal is located in the middle of the three pedals. This pedal is used to hold out only notes that are pressed when first lowering the pedal but will not let any following notes that are to be played to continue to ring.
On most vertical pianos the middle pedal is used as a practice mute. When the pedal is depressed a piece of cloth or felt will be lowered in front of the strings. As a note is played with this pedal in use the sound is extremely soft and muffled. This is a great pedal to use during practice when a student doesn’t want to have the piano at full sound. A great example of this is when a student wants to practice late at night and not wake anyone in the home.
The pedal to the left is called the Una Corda pedal. This is another pedal used to change the  loudness of the piano. On a grand the keyboard will shift to the right when the pedal is pressed. Inside the piano when a key is played a hammer will hit the three strings but when the Una Corda pedal is used it causes the hammer to hit only one string instead of all three. It is used to help the student play soft passages. On a vertical piano the hammers are moved closer to the strings when the pedal is being pressed. This again is a way to help the student play softer by having to use less force to get the hammer to the strings.